Two new antioxidant active polyketides from Penicillium citrinum, an endolichenic fungus isolated from Parmotreama species in Sri Lanka

Bioassay guided fractionation of the ethyl acetate extract of a laboratory culture of Penicillium citrinum, an endolichenic fungal strain isolated from a Parmotrema species in Sri Lanka, led to the isolation of two new fungal polyketides (1 and 2). The structures of these compounds were determined on the basis of their 1D NMR, 2D NMR and FABMS spectroscopic data. The two compounds (1 and 2) showed radical scavenging activity with IC50 values of 159.7 ± 22.3 μg/mL and 68.6 ± 4.3 μg/mL, respectively in DPPH antioxidant assay. The antioxidant activity of compound 2 was comparable to the standard antioxidant compound butylated hydroxytoluene (BHT).